High-temperature grease



l atentecl Feb. 12, 1952 UNITED STATES PATENT OFFICE I 2,585,321 V V HIGH-TEMPERATURE GREASE Richard A. Butcosk, Jackson Heights, N. Y., as- Signor to SOcony-Vacuum OilConipany, Incorporated, a corporation of New York NoDrawing. Application June 13,1950, Serial No. 167,935

-9 Claims. 3

This invention has 'to do with greases characterized by a high order of effectiveness under severe operating conditions, particularly for service at temperatures ranging from 400 F. to 500 F. and higher. g 7

It is well known that greases lose some or all of their effectiveness when subjected to high temperature operations. In lubricating machine parts, for example, it is essential that a grease retain its gel structure during use; failure to do so results in high consumption of the grease and frequent servicing. In general, available greases suffer from a marked tendency to change in character when used over a wide range of temperature, particularly at high temperatures of the order of 400-500 F. and higher. Some conventional greases are characterized by excessive softening when exposed to such high temperature operation, thereby being extruded too rapidly from the area being lubricated to provide efiicient lubrication.

It is an object of this invention, therefore, to provide a grease effective for high temperature use, such as at 400-500" F. and higher. A further object is to provide a grease which retains its original character over a wide range of operating conditions. Other objects of the invention will be apparent from the following description.

It has now been discovered that lithium base greases containing an ester of a phosphoric or phosphorous acid in certainproportions, are sub- 1 tributyl phosphate, triphenyl phosphate, tricresyl stantially free of the shortcomings referred to above. The greases contemplated herein have a lithium soap content-of the order of 5-25 per cent on the basis of the finished grease. 'Fats and fatty acids which can be used are those generally found in soap type grease. Such fatty materials have from about 12 to about 22 carbon atoms per molecule. Representative of such materials are vegetable, animal and fish fatty oils, and hydrogenated fatty materials thereof. Stearin, stearic acid, cottonseed oil acids, oleic acid, palmitic acid, myristic acid, hydrogenatedfish oilssuch as Hydrogenated Fish Oil, Iodine No. '77 and Hydrofol, are" typical. A preferred soap herein is lithium stearate. Methods of preparation of lithium soaps are well known in the art and discussion of the same is-believed to be unnecessary. The mineral oil constituent of the greases of this invention are those suitable for use at high temperatures. The oil can vary considerably in character; for example, it can be a residual 'or distilled oil. The oil constituent, however, is characterizedby a viscosityiS. U. V.) of greater phosphate and triphenyl phosphite, Another es: ter suitable for use here is tri-tertiaryeamyl phenyl nh sph e M. a

As indicated above, the proportions of lithium soap and phosphorus ester are balancedlin order to provide greases of the desired character. The lithium soap or soaps comprise from about 5-25 per cent (by weight) of the'finished grease, and preferably from. about 8 per cent to a maximum of 18 per cent. The phosphorus ester or esters present in the grease will range from about 10, to

' about 50 per cent (by weight) of the greaseproduct, and preferably from about 1'7 percent to about 30 per cent. Increasingthe ester content tends to make the grease firmer at temperatures of the order of 400-500 F., in addition to the firm consistency at lower temperatures, 'With more than about 50 per cent by Weight of a phosphorus ester in the grease, however, there is a marked tendency for the grease to become hard during service, thereby having lower lubricating value. Moreoven-whenfio per cent or more of a phosphorus ester is use'd'with the aforementioned quantities of lithium soapglittle if any im provement-in dropping point is realized. Greases with less than'about 5% of lithium's'oap-seem to have very little mechanical stability and are usually semi-fluid in nature. Greaseswith more than 25 of lithiurnsoap are. quite expensive, and are to'o firm or are block form and not satisfactory foruse as ball bearing lubricants. The balance of the grease is mineraLoil of the character described above. Accordingly, the various constituents (ona-dry basis) of the new greases Itis to be understood that thegreases of invention can alsfocontain other characterizing materials and fillers, so long as the foregoing balance between the, lithiumsoap andphosphorus ester is maintained. For example, the greases can contain grease antioxidants such as amines, phenols, sulfides, etc.; fillers such as asbestos, graphite, mica, talc, etc. and lubricity improving agents such as free fat, free fatty acids, esters of alkyl and/or aryl acids, sulfurized fats, lead soaps, etc.

The new greases are prepared by dissolving a lithium soap in mineral oil at a temperature above about 230 F. The mixture foams as the 4 by grease 4, namely, alkaline character. This is of value inasmuch as the grease is resistant to oxidation.

I claim:

5 1. A high temperature grease consisting essentially of: mineral oil, a lithium soap content of from about 5 to about 25 per cent by weight, and about to about 50 per cent by weight of an ester of an oxy-acid of phosphorus, said grease soap dissolves, indicating evaporation of water. n retaining its original gel structure at tempera- When all foaming has ceased, a phosphorus ester is added and the resulting mixture is stirred and heated at 430 F. for or 30 minutes. The product is then withdrawn from the vessel in which tures ranging from 400 F. to 500 F.

2. A high temperature grease consisting essentially of: mineral oil having an S. U. V. from about 100 to about 2,000 seconds at 100 F., a

t is p pa a n into a suitable mold- The 15 lithium soap content of from about 8 to about grease is allowed to cool whereupon it solidifies.

The solid grease can then be cut into cakes of the desired size, and milled to desired consistency.

The greases of this invention are illustrated by 18 per cent by weight, and about 17 to about 30 per cent by weight of an ester of an oxy-acid of phosphorus.

3. A high temperature grease consisting essenthe followin xamp s ta u t d in the table -20 tially of: about 50 per cent by weight of a minbelow. Provided also in the table are comparable examples in which diflerent metal soaps are used instead of a lithium soap; however, all soaps are stearates. Another comparable example involves a thiophosphate ester in place of a phosphate or phosphite ester. Each of the greases shown in the table was prepared according to the procedure described above.

eral oil having an S. U. V. of 1,000 seconds at 100 F., about 20 per cent by weight of lithium soaps, and about per cent by weight of tricresyl phosphate.

4. A grease as defined by claim 1 wherein the ester is a phosphoric acid ester.

5. A grease as defined by claim 1 wherein the ester is a phosphorous acid ester.

Table Grease No 1 2 3 4 5 6 7 s 9 1o Composition:

Mineral Oil 50 50 50 50 50 50 50 50 50. 3O 30 30 30 30 30 30 30. Phosphorus Comtricresyl triphenyl tributyl triphenyl tricresyl tricresyl tricresyl tricresyl tricresyl triphenyl pound. phosphosphosphosphosphate phosphosphate phosphosthiophate. phate. phate. phitc. phate. phate, phate pgosite. Soa 20 20 20 20? P Mettal Base Lithium. Lithium Lithium. Lithium Aluminum Calcium. Magnesium Lead. Sodium Lithium.

roper ies:

AS T l\/ItD r%pping 500-|- 487 459 500+"--- 240 210 liquid 500+--." Liquid--- 403.

0111 Approximate 150 200 230 220 semi-fluid. semifluid. liquid 220.

Penetration (Unworked). Structure Short Short Short Short Grainy Buttery.

Fibre Fibre. Fibre Fibre and mushy. Neutralization 03 014 03 Alkalin- 0.14.

No. mgms ity 1.4 KOH/g (ASTM) l 100 Sec. S. U. V. at 100 F.

It will be noted from greases 1-4 that the lithium soaps and the phosphate and phosphite esters cooperate to provide a high dropping point and excellent penetration value. In this connection, it appears that aryl phosphates are more advantageous than alkyl phosphates, as shown by a comparison of greases 1, 2 and 3. In sharp contrast with these greases are those identified as 5 through 9, in which lithium has been replaced by aluminum, calcium, magnesium, lead 0 and sodium, respectively. All of the latter greases failed to retain their character at high temperatures, that is, the soaps and liquid phase did not hold together and did not produce the desired gel structure. Although grease 8, involv- 5 ing a lead soap, is characterized by an excellent dropping point value, it is of poor structure.

Grease 10 in which the ester is a thiophosphite, is shown for comparison with grease 4 in which the ester is the corresponding phosphite. 7 2,339,924

The structure of grease 10 is not retained at high temperature, and the dropping point is substantially less than that which characterizes grease 4.

An additional desirable feature is manifested 6. A grease as defined by claim 2 wherein the ester is tricresyl phosphate.

7. A grease as defined by claim 2 wherein the ester is triphenyl phosphate.

8. A grease as defined by claim 2 wherein the ester is tributyl phosphate.

9. A grease as defined by claim 2 wherein the ester is triphenyl phosphite.

RICHARD A. BUTCOSK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

